Class::Load - A working (require "Class::Name") and more
version 0.25
use Class::Load ':all';
try_load_class('Class::Name')
or plan skip_all => "Class::Name required to run these tests";
load_class('Class::Name');
is_class_loaded('Class::Name');
my $baseclass = load_optional_class('Class::Name::MightExist')
? 'Class::Name::MightExist'
: 'Class::Name::Default';
"require EXPR" only accepts "Class/Name.pm" style module
names, not "Class::Name". How frustrating! For that, we provide
"load_class 'Class::Name'".
It's often useful to test whether a module can be loaded, instead of throwing an
error when it's not available. For that, we provide "try_load_class
'Class::Name'".
Finally, sometimes we need to know whether a particular class has been loaded.
Asking %INC is an option, but that will miss inner packages and any class for
which the filename does not correspond to the package name. For that, we
provide "is_class_loaded 'Class::Name'".
"load_class" will load "Class::Name" or throw an error, much
like "require".
If "Class::Name" is already loaded (checked with
"is_class_loaded") then it will not try to load the class. This is
useful when you have inner packages which "require" does not check.
The %options hash currently accepts one key, "-version". If you
specify a version, then this subroutine will call
"Class::Name->VERSION( $options{-version} )" internally, which
will throw an error if the class's version is not equal to or greater than the
version you requested.
This method will return the name of the class on success.
Returns 1 if the class was loaded, 0 if it was not. If the class was not loaded,
the error will be returned as a second return value in list context.
Again, if "Class::Name" is already loaded (checked with
"is_class_loaded") then it will not try to load the class. This is
useful when you have inner packages which "require" does not check.
Like "load_class", you can pass a "-version" in %options. If
the version is not sufficient, then this subroutine will return false.
This uses a number of heuristics to determine if the class
"Class::Name" is loaded. There heuristics were taken from
Class::MOP's old pure-perl implementation.
Like "load_class", you can pass a "-version" in %options. If
the version is not sufficient, then this subroutine will return false.
This attempts to load the first loadable class in the list of classes given.
Each class name can be followed by an options hash reference.
If any one of the classes loads and passes the optional version check, that
class name will be returned. If
none of the classes can be loaded (or
none pass their version check), then an error will be thrown.
If, when attempting to load a class, it fails to load because of a syntax error,
then an error will be thrown immediately.
"load_optional_class" is a lot like "try_load_class", but
also a lot like "load_class".
If the class exists, and it works, then it will return 1. If you specify a
version in %options, then the version check must succeed or it will return 0.
If the class doesn't exist, and it appears to not exist on disk either, it will
return 0.
If the class exists on disk, but loading from disk results in an error (e.g.: a
syntax error), then it will "croak" with that error.
This is useful for using if you want a fallback module system, i.e.:
my $class = load_optional_class($foo) ? $foo : $default;
That way, if $foo does exist, but can't be loaded due to error, you won't get
the behaviour of it simply not existing.
Because of some of the heuristics that this module uses to infer whether a
module has been loaded, some false positives may occur in
"is_class_loaded" checks (which are also performed internally in
other interfaces) -- if a class has started to be loaded but then dies, it may
appear that it has already been loaded, which can cause other things to make
the wrong decision. Module::Runtime doesn't have this issue, but it also
doesn't do some things that this module does -- for example gracefully handle
packages that have been defined inline in the same file as another package.
- <http://blog.fox.geek.nz/2010/11/searching-design-spec-for-ultimate.html>
- This blog post is a good overview of the current state of
the existing modules for loading other modules in various ways.
- <http://blog.fox.geek.nz/2010/11/handling-optional-requirements-with.html>
- This blog post describes how to handle optional modules
with Class::Load.
- <http://d.hatena.ne.jp/tokuhirom/20110202/1296598578>
- This Japanese blog post describes why DBIx::Skinny now uses
Class::Load over its competitors.
- Moose, Jifty, Prophet, etc
- This module was designed to be used anywhere you have
"if (eval "require $module"; 1)", which occurs in many
large projects.
- Module::Runtime
- A leaner approach to loading modules
Bugs may be submitted through the RT bug tracker
<
https://rt.cpan.org/Public/Dist/Display.html?Name=Class-Load> (or
[email protected] <mailto:
[email protected]>).
There is also a mailing list available for users of this distribution, at
<
http://lists.perl.org/list/moose.html>.
There is also an irc channel available for users of this distribution, at
"#moose" on "irc.perl.org"
<irc://irc.perl.org/#moose>.
Shawn M Moore <sartak at bestpractical.com>
- •
- Dave Rolsky <[email protected]>
- •
- Karen Etheridge <[email protected]>
- •
- Shawn Moore <[email protected]>
- •
- Jesse Luehrs <[email protected]>
- •
- Kent Fredric <[email protected]>
- •
- Paul Howarth <[email protected]>
- •
- Olivier Mengué <[email protected]>
- •
- Caleb Cushing <[email protected]>
This software is copyright (c) 2008 by Shawn M Moore.
This is free software; you can redistribute it and/or modify it under the same
terms as the Perl 5 programming language system itself.